Bag-in-containers, also referred to as bag-in-bottles or bag-in-boxes depending on the geometry of the outer vessel, all terms considered herein as being comprised within the meaning of the term bag-in-container, are a family of liquid dispensing packaging consisting of an outer container comprising an opening to the atmosphere the mouth and which contains a collapsible inner bag joined to said container and opening to the atmosphere at the region of said mouth. The system must comprise at least one vent fluidly connecting the atmosphere to the region between the inner bag and the outer container in order to control the pressure in said region to squeeze the inner bag and thus dispense the liquid contained therein.
Traditionally, bag-in-containers were and still are produced by independently producing an inner bag provided with a specific neck closure assembly and a structural container (usually in the form of a bottle). The bag is inserted into the fully formed bottle opening and fixed thereto by means of the neck closure assembly, which comprises one opening to the interior of the bag and vents fluidly connecting the space between bag and bottle to the atmosphere; examples of such constructions can be found inter alia in U.S. Pat. Nos. 3,484,011, 3,450,254, 4,330,066, and 4,892,230. These types of bag-in-containers have the advantage of being reusable, but they are very expensive and labour-intensive to produce.
More recent developments focused on the production of “integrally blow-moulded bag-in-containers” thus avoiding the labour-intensive step of assembling the bag into the container, by blow-moulding a polymeric multilayer preform into a container comprising an inner layer and an outer layer, such that the adhesion between the inner and the outer layers of the thus produced container is sufficiently weak to readily delaminate upon introduction of a gas at the interface. The “inner layer” and “outer layer” may each consist of a single layer or a plurality of layers, but can in any case readily be identified, at least upon delamination. Said technology involves many challenges and many alternative solutions were proposed.
The multilayer preform may be extruded or injection moulded (cf. U.S. Pat. No. 6,238,201, JPA10128833, JPA11010719, JPA9208688, U.S. Pat. No. 6,649,121). When the former method is advantageous in terms of productivity, the latter is preferable when wall thickness accuracy is required, typically in containers for dispensing beverage.
Preforms for the production of integrally blow-moulded bag-in-containers clearly differ from preforms for the production of blow-moulded co-layered containers, wherein the various layers of the container are not meant to delaminate, in the thickness of the layers. A bag-in-container is comprised of an outer structural envelope containing a flexible, collapsible bag. It follows that the outer layer of the container is substantially thicker than the inner bag. This same relationship can of course be found in the preform as well, which are characterized by an inner layer being substantially thinner than the outer layer. Moreover, in some cases, the preform already comprised vents which are never present in preforms for the production of co-layered containers (cf. EPA1356915).
The formation of the vents fluidly connecting the space or interface between bag and bottle to the atmosphere remains a critical step in integrally blow-moulded bag-in-containers and several solutions were proposed in e.g., U.S. Pat. Nos. 5,301,838, 5,407,629, JPA5213373, JPA8001761, EPA1356915, U.S. Pat. No. 6,649,121, JPA10180853.
One redundant problem with integrally blow-moulded bag-in-containers is the choice of materials for the inner and outer layers which must be selected according to strict criteria of compatibility in terms of processing on the one hand and, on the other hand, of incompatibility in terms of adhesion. These criteria are sometimes difficult to fulfil in combination.
The preform usually consists of an assembly of two separate preforms and produced independently from one another and thereafter assembled such that the inner preform fits into the outer preform as illustrated in JPA10180853. This solution allows for greater freedom in the design of the neck and vents, as well as in the choice of materials for the inner and outer layers: the compatibility in terms of processing between the materials of the inner and outer layers concern the blow-moulding operation only. It is, however, expensive as it requires two separate production lines and an assembly line.
Replacing a preform assembly as discussed above by an integral preform obtained by injection moulding one layer on top of the other offers of course a number of potential advantages in terms of production costs. Other problems, however, arise and need be addressed. In particular, the choice of materials for the inner and outer layers is more complex since they must be compatible in terms of process in both the injection moulding and the blow-moulding operations. U.S. Pat. No. 5,301,838 discloses a complex injection moulded, five layer, integral preform comprising three PET layers interleafed by two thin layers of a material selected from the group of EVOH, PP, PE, PA6. This solution, however, is quite complex and requires that the materials of the thin layers have “little if any primary affinity for (i.e;, tendency to chemically bond or adhere to) the adjacent [PET] layers,” which unduly restricts the choice of materials to be used.
EPA1356915 and U.S. Pat. No. 6,649,121 proposes that the materials for the inner and outer layers of the preform should be selected such that the melting temperature of the outer layer is higher than the one of the inner layer, Tm,outer>Tm,inner, lest a strong bond would form between layers when the inner layer is injection moulded over the outer layer, which had been injected into the mould cavity first. Examples of materials for the outer layer given by the authors include PET and EVOH, whilst polyethylene is given as an example for the inner layer.
It follows from the foregoing that there remains room in the art for solutions for the production of integral preforms made of materials compatible in terms of processing, both for the injection moulding and blow-moulding operations, and yielding bag-in-containers with good delamination properties.